An idler includes a pulley that transmits no power but guides or tensions a belt. The pulley is rotatable about a shaft and rests on or presses against a drive belt to guide it or take up slack. In a vehicular application, an idler pulley can be used as part of a vehicle's pulley assembly to help regulate how the belts run from a motor shaft to generate movement in other parts and engine accessories. Thus, the belt can rest on the idler pulley as well as other pulleys. The idler pulley can be operatively arranged between a drive pulley and a driven pulley.
Vehicle power assist systems, such as brake boost actuators and electric power steering systems, can include the pulley assembly having the idler. To transfer the output of the electric motor to the steering gear assembly or brake boost, the drive pulley is connected to the output of the electric motor, and the driven pulley is connected to the steering gear assembly or brake boost. The belt may be a flat belt, a cog belt, or a vee belt. Belt drives may require some means of maintaining tension in the belt, and thus the idler pulleys have been used on the slack side of the belt to apply a nearly constant tension as the belt stretches under load.
FIG. 1 shows a conventional idler 1 in relation to a belt 2 to be tensioned. The idler 1 includes an idler pulley 3, a ball bearing 4 (details not shown) with a ball bearing axis 5, a screw 6 with a screw axis 7, and an eccentric cam (radially interior of the idler pulley 3). In such an arrangement, both the eccentric cam and the idler pulley 3 must be custom machined, which adds to the cost of the idler 1. The screw 6 is both a pivot point for the eccentricity and a clamp. Rotation of the eccentric cam about the screw axis 7 causes the bearing axis 5 to move closer to the belt 2. The belt 2 is contacted by the idler pulley 3, which is pressed onto the bearing 4. Thus, eccentric rotation of the idler 1 on the eccentric cam tensions the belt 2. The ball bearing 4 is used to prevent end faces of the idler pulley 3 from rubbing against a housing.
It is desirable to provide a pulley system with an idler that is more cost effective than conventional idlers while still enabling the proper tension on the belt.